DE961090C - Method and device for separating low-boiling gas mixtures - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

ISSUED APRIL 4, 1957

GERMAN PATENT OFFICE

PATENT LETTERING

CLASS 17g GROUP 2oi INTERNAT. CLASS F 25j

U 3334Ia-117 g

Lawrence Donald Potts, Eggertsville, N. Y., and Edward Freemann Yendali, Kenmore, N. Y. (V. St. A.)

have been named as inventors

Union Carbide and Carbon Corporation, New York, N.Y. (V. St. A.)

Method and device for separating low-boiling gas mixtures

Patented in the territory of the Federal Republic of Germany on May 3, 1955 Patent application published October 11, 1956

Grant of patent announced on March 21, 1957 The priority of the application in the V. St. v. Claimed America May 4, 1954

The invention relates to a method and an apparatus for separating low-boiling points Gas mixtures and relates in particular to a double one Pressure circuit for the separation of air into its main components for the extraction of different ones Quantities of liquid and gaseous oxygen and of oxygen of various purities.

When separating air into its main components, it is desirable that the separation products,

in particular the oxygen obtained, the wishes of the consumer in terms of purity, physical Condition and consumption rate largely correspond. The previous air separation systems were used for the production of either liquid or gaseous oxygen. Attachments for the Liquid and gaseous oxygen production have usually been inadequate and inadaptable regarding any change to the

Ratio of liquid to gaseous production. For this reason, the Heylandt cycle process with high compressed air can only be more liquid Oxygen can be obtained effectively, while low-level compressed air circulation method according to Frankl only can be used effectively for the production of gaseous oxygen.

Often the businesses of the consumers are so diverse that both liquid and gaseous ίο oxygen are required in different amounts by a single air separation system. Such adaptability of the operation brings with it significant difficulties in establishing an effective cycle process. Some plants are so diverse that both low purity oxygen (about 95 ° / ₀ ) and high purity oxygen (about 99.6 ° / ₀ and more) can be used economically. The relative consumption rates for low and high purity oxygen can also be different. So z. For example, a sudden change in operational schedules may require an equally sudden increase or decrease in the consumption of high or low purity oxygen, or any combination of such consumption. Such changing production requirements create serious difficulties in partitioning an effective cycle to cope with all of these situations.

For the effective production of only liquid oxygen of high purity, the Systems or circulation processes according to Heylandt used. These require high initial air pressure and work with expansion in the production of external work of a large part of the high pressure air, before it was frozen.

The so-called Frankl system is used for the effective extraction of only gaseous oxygen of low purity. In such cycle processes, the initial air pressure is approximately 5.27 kg / cm ² above atmospheric pressure; the air is cooled by means of cold accumulators, while the cooling is effected by the expansion work of part of the deep-frozen air. To obtain liquid oxygen, a modification of the Frankl cycle process has been proposed, in which the increased requirements for cooling are met by expansion work of a larger part of the air, namely the so-called excess air, which cannot be subjected to separation and thus on Performance is lost.

The so-called Linde-Frankl cycle process represents an improvement of the Frankl method. According to this method, an additional High-pressure air flow for itself indirectly cooled and via a throttle to the rectification column to ensure the self-cleaning effect of the cold Batteries released. This can be referred to as the "double pressure cycle process" at which the expansion of the high pressure stream only requires cooling for the production of gaseous Oxygen covers. After a possible reorganization for simultaneous liquid extraction such a cycle process would be ineffective and lack the desired adaptability.

According to a proposal for the production of oxygen, also of high purity, using the Linde-Frankl process an auxiliary rectification column should be used for the main production of low-purity oxygen with heat exchangers connected to it and a compressor for compressing a part of low-purity oxygen as well as for cooling, liquefying and rectifying the same for production of a gaseous product of high purity can be added. This latter procedure is also not for an effective production of different amounts of liquid and gaseous oxygen suitable and, moreover, conditionally expensive for the production of high-purity oxygen Refurbishments and additional equipment.

Accordingly, there is a need for a new cycle process of the double pressure type with which the limited possibilities of previous methods for effective and adaptable extraction of liquid as well as gaseous oxygen in the desired ratio to each other as well as for the Obtaining both high and low purity gaseous oxygen avoided in the desired amount when using a single two-stage rectifying column will.

It is therefore an essential aim of the present invention to provide an improved double pressure cycle process for the separation of gaseous mixtures, such as air, in which both liquid and gaseous products, such as B. Oxygen, can be obtained simultaneously and effectively can.

Another object of the present invention is to provide a dual pressure cycle process for the separation of an air mixture with which the use of only a single exchanger or a single rectifier for a wide range of gas requirements.

It is further contemplated by the invention to provide a double pressure cycle process for separation of air into its components, which has the properties of an adaptable company for has a wide range of material requirements for the simultaneous production of different quantities liquid and gaseous oxygen of various purities.

The present invention therefore relates in particular to a method for separating low-boiling points Gas mixtures by rectification at low temperature, at which gas mixture flows are provided under condensation pressure and under high pressure, the stream under condensation pressure by heat exchange with., a part of the Separation product is cooled to a temperature close to its condensation temperature, while a first part of the high pressure flow is cooled to the condensation pressure by expansion work and a second part of the high pressure flow through heat exchange including a heat

exchange cooled with another part of the separation product to a low temperature and the second part cooled in this way expands to the condensation pressure and one part Liquefaction of the vapor parts of the resulting streams under condensation pressure is effected in order to to ensure hydration for rectification.

According to the invention, the method is essentially characterized in that the non-liquefied remainder is superheated to such a temperature becomes that it is in a dry, saturated state after expansion work to rectification pressure is located and then the superheated steam expands, as well as that the proportional release of the gaseous • and liquid separation products by passing adjusted amounts of the expanded Steam for rectification as well as to the outflowing, lower-boiling product of the rectification is controlled and / or by regulating the proportional amount of the supplied under high pressure Gas mixture to the supplied under condensation pressure.

The invention also relates to a device for carrying out the method described.

According to a preferred embodiment, to vary the relative amounts from under high and low pressure air an additional compressor of different capacities for treatment the amount of high pressure air used. All of the air supplied is initially in one Low-pressure compressor compresses, whereupon part of the outflow quantity as low-pressure flow to the low-pressure air cooling system is fed. The variable remainder is further compressed to form the high pressure flow in the additional machine.

To achieve maximum performance, the low-pressure air flow is cooled and through heat exchange with the cold separation products in periodically reserved cold regenerators or cold accumulators cleaned. The high pressure part is split into two streams in one way similar to the Heylandt cycle process, with a high pressure flow indirectly counter-rotating under high pressure is cooled while the remainder of the stream is used in an expansion machine for external work Cost of internal energy is dealt with. All gas flows are combined in one Scrubbers or gas scrubbers to remove residual carbon dioxide and other contaminants treated, whereby part of the scrubbed gas is turbo-expanded to meet the requirements of the Procedure in terms of cooling to correspond to low temperature. The scrubber and the Rectifying columns can optionally be connected to one another.

To the other essential features and advantages of the combination of elements of the cycle process according to the invention include, inter alia: i. A high pressure air stream can be in usual Way to heat up the gas part fed to the turbo-expander by countercurrent exchange use. This avoids difficulties such. B. the above Necessity of using a tap or shunt current from one serving this purpose Low pressure regenerator. Accordingly, significant economic savings are realized by that a smaller and cheaper preheat exchanger can be used.

2. The requirement for a regenerator bypass airflow According to Frankl is also not applicable because the other reason for its application, namely the creation of heat imbalance for self-cleaning regenerators, through a easier means is achieved. The present combination of systems low and high Pressure to supply air to the columns results in the passage of a quantity of the cold rectification product through the regenerators according to the amount of air that is passed through the regenerators flows to ensure that deposits do not accumulate. In this way they lie Conditions so that the cold rectification products are capable of everything through the incoming Air-separated water and carbon dioxide are completely removed with them, thereby reducing the Clean regenerators yourself during operation.

3. The system is also particularly suitable for generating gaseous oxygen of high purity. The cold, gaseous oxygen product of high purity can be produced indirectly by counter-rotating Heat exchange with a stream of incoming high pressure air. This warming can also be effected by indirect heat exchange coils connected to the regenerator.

In any event, the high purity product is not contaminated with residual air.

4. The new system can also be adjusted to a large range of changes in gas demand Avoid the difficulties associated with operating a simple low pressure oxygen cycle process occur according to Frankl when the gas demand suddenly drops. These difficulties include e.g .:

a) Excess gas generation can be released into the atmosphere, but what about the operating costs would be unsuitable.

b) Excess gas generation can be stored as gas for later purposes, which, however would require very high investment costs.

c) The supply of air to the plant can be reduced, which is from the standpoint of operating costs is more favorable, but a strong limitation of the determined by the compressor or the rectifying column Air supply volume with it, because most air centrifugal compressors do not fall below 50% their capacity work and because the rectification column of this procedure is the most important limitation opposed. Even if the amount of air compression is to any desired level could be reduced, the column would possibly only process so little air that it because of the inadequate level of liquid in troughs

etc. would not work properly. This can e.g. B. at about 35% of the estimated air volume occur, so any decrease in consumption below 35% of the normal level will result in storage 5 or rejection of the excess gas.

d) Excess air can be diverted from the turbo-expander to the excess product Liquefied for storage purposes like liquid oxygen. The process of obtaining liquid by expansion of excess air is more expensive than the recovery of liquid according to a conventional one Heylandt high pressure system. Another disadvantage is that most of the Turbine capacity is required to heat the incoming air and little to extract the air Liquid remains.

A major advantage of the double pressure cycle process according to the present invention is that all of the high-pressure air is passed on to the column and none of it is branched off to the turbo-expander needs to be so that a sufficiently high air pressure can be supplied to the To keep the column operating even when no gaseous oxygen product is obtained. On the other hand, the high-pressure air system can have a high demand for gaseous oxygen derived so that the use of the entire operating capacity of the column for oxygen production allows. It follows that the double pressure circuit according to the present Invention enables a wide operating range for gas extraction.

5. The system according to the invention also allows an almost continuous adjustment such that changing requirements for gaseous oxygen can be met. Although the amount of High pressure air supply can only be adjusted gradually, the system can in the case of medium Required quantities work by changing the amount of air through the turbo expander. This means, that the system may not perform at its maximum capacity for certain requirements would work, but the amount of liquid produced by the application of the "excess air" based operating mode can be kept relatively small if there are enough "levels" for the high pressure air supply are provided.

Another feature of the invention is that in a simple manner a laterally attached Condenser is provided to adjust the ratio of liquid to air in the Oxygen production contributes.

Furthermore, means for cooling a high-pressure air stream can be very advantageously multiply Provide sections with novel means of heating a washed stream of air vapor relatively low pressure in one of the sections for subsequent expansion in one Expansion device, the state of the high pressure air before entering this section is such, that the desired heating of the amount of air vapor to be expanded is effected. 1

Further features of the invention are evident from the representations of exemplary embodiments and from can be found in the following description. It shows Fig. Ι a schematic view of a double print arrangement for separating air according to the present invention and

FIG. 2 is a view, essentially similar to ^{FIG. 1} , of a modified embodiment.

All of the pressure values given below are measured values above atmospheric pressure.

According to FIG. 1, a gas mixture, for. B. ordinary atmospheric air, into the system at two different pressure levels, namely a low pressure between 4.21 and 7.03 kg / cm ² , preferably about 5.27 kg / cm ² , and a high pressure between 70.3 and . 211 kg / cm ² , preferably about 140 kg / cm ² . Expediently, all of the air supplied is first compressed in a compressor unit 10 and released under a relatively low pressure of approximately 5.27 kg / cm ² . Part of this air under low pressure enters the cooling separation system through an air inlet duct 11, while the remainder is further compressed in the desired amount to a relatively high pressure for subsequent introduction into the separation system, as will be described further below.

Because gaseous impurities in the air, which have higher boiling points than oxygen, are used for the liquefaction and rectification of the air applied freeze and thereby the Obstructing the continuity of the air separation circuit, according to the present invention, the under low The pressurized part of the air is cooled and the separation products in periodically reversed cold Accumulators or regenerators 12, 13, 14 or 15 reheated. During such cooling of the air, moisture and carbon dioxide become solids in the form of ice or the like. Deposited on the inner surface area of the regenerators, whereupon after the "reversing" of the regenerator the frozen separation by the in uiagekefaier 1-05 Direction of the separation products is removed. As illustrated, there are four regenerators provided, but it can also be more or less, the regenerators 12, 13 preferably by a secreted gaseous oxygen product, the regenerators 14, 15 preferably by a secreted nitrogen gas can be cooled.

To completely remove any carbon dioxide particles that may still be in the air, the air is further in a corresponding scrubber or gas scrubber 17 before entering the exchange system cleaned. For this purpose, the air cooled by the regenerator is passed through the regenerator air lines 18 and 19 are delivered to the scrubber inlet line 20 and then into the lower section of the scrubber iao unit 17 led.

The scrubber 17 is conventional and has an elongated, generally cylindrical Container with a space for absorbing liquid at its lower end and condensing or liquefaction coils 21 and 22 in the one above

located room, the segregated gas products, z. B. oxygen or nitrogen. The air cooled by the regenerator is discharged into the scrubber 17 at or near its bottom and flows through a bath of washing or scrubbing liquid, which consists of oxygen-rich liquefied air. This scrubbing liquid is passed through a line 23 controlled by a throttle valve 24 and further through a contaminant removal system which has a filter 25 for removing solid contaminants including carbon dioxide particles. A reserve _{filter 25 a} is shunted to the filter 25 and enables cleaning or removal and replacement of the filter 25 without interrupting the flow of washing liquid. The liquefaction coils 21 and 22 generate liquid for washing the incoming air by condensing part of the washed air.

A portion of the pure steam in the scrubber 17 is passed through an outlet line 26 for washed air steam sent to the rectification column, while another part is preferably sent through the steam line 27 is fed to a condenser 28 for heat exchange, where it condenses if necessary, and then is fed back to the scrubber 17 as liquid air through a return line 29, namely in this Case as an additional treatment liquid.

The remaining part of the clean, scrubber washed steam in the scrubber 17 is through a Line 30 led to the execution of thermodynamic functions, such as. B. Cooling and refrigeration by expansion to increase the performance of the air separation circuit, and then completely or partially released into the rectification, as described below.

The oxygen and nitrogen separation products in the coiled tubes 21 and 22 are with the lower ones or cold ends of the oxygen regenerators 12 and 13 and the nitrogen regenerators 14 and 15, respectively brought by means of lines 31 and 32 in connection.

A variable capacity compressor 40 takes in low pressure air from line 11 at its inlet end at a pressure of about 5.27 kg / cm ² and preferably supplies it at a relatively high pressure between 84.3 and 211 kg / cm ² 140 kg / cm ² , to a pre-cooling channel 41 for heat exchange with a counter-flowing part of the separate nitrogen supplied to the pre-cooling channel 42 through the line 43.

Another section for cooling the compressed air at high pressure is realized in a conventional, externally cooled precooler 44 where the temperature of the high pressure air is lowered to about -40 ^0th Ammonia, carbon dioxide and a commercially available fluorohydrocarbon coolant are examples of coolants that can be used for this purpose. Usually two such pre-coolers are provided so that the moisture frozen out of the air can be removed by defrosting one cooler while the other is in operation.

Air is split into two streams by precooler 44, one stream being fed through high pressure air line 46 to a reciprocating expansion cylinder 47 where it ^{expands to a lower pressure of approximately 5.27 kg / cm 2} and discharged through line 48 which combines with the air compressed to low pressure in the inlet line 20 of the scrubber to increase the air supply to be freed from impurities in the scrubber 17. The other stream of split, high-pressure compressed air is discharged into a channel 50 of a countercurrent heat exchanger C, where the air is cooled in heat exchange with channels 51 and 52 which contain countercurrent high-purity oxygen and nitrogen gas products flowing out.

In the arrangement shown in FIG. 1, a larger part of the separate gaseous nitrogen products in line 32 is used for cooling the regenerator air which is under relatively low pressure. ¹ The remaining and at the same time smaller part of the separate nitrogen gas is used to cool part of the high-pressure air. As a result, the main stream of nitrogen gas flows in line 32 to regenerators 14 and 15, while the smaller stream flows through a countercurrent branch line 54 which is connected to channel 52. After heating the nitrogen in channel 52 by cooling the air in channel 50, the nitrogen is released to precooler 42 through line 43, whereupon the heated nitrogen can be used further or simply released into the atmosphere.

For the further. Additional means are provided for cooling the high-pressure air stream emerging from the countercurrent channel 50. For this purpose, the high-pressure air flow is introduced into a turbine preheating exchange duct 53, where the temperature of the air is further reduced by heat exchange with the cold air vapor in line 130, which has been washed in the scrubber. This cooled high pressure air is then expanded through a valve 55 to 3.87 to 5.27 kg / cm ^{2 in} order to increase the supply of the low pressure air in the inlet line 20 of the scrubber. *

The heated and washed air vapor exiting the turbine preheat exchanger 53 becomes passed through a line 56 to the inlet of an expansion turbine 57. The one obtained from the turbine external work is preferably carried out using a corresponding coupling connection of the turbine used an electric generator. The cooling obtained is used in the system.

Since some of the air may liquefy during the expansion in the turbine, the air to be expanded is heated in the turbine preheater to such a temperature that the turbine suction is as close as possible and not below the temperature of its dry saturation. If necessary, clean air from the scrubber line 30 can be fed directly to the turbine 57 via a bypass valve 3O _a for better control of the temperature.

The rectification of the liquid and gaseous Air is realized in a conventional rectifying column 59, which is relatively large in size may have. As shown in FIG. 1, the rectifying column 59 is of the common double column type having a lower elongated high pressure rectifying column chamber 60, an upper elongated one 'Low pressure rectifying column 61, which is above the lower Column is arranged, and a main condenser 62, which the high pressure chamber 60 from the upper Locks the low pressure rectification column. The main capacitor 62 is provided with vertical tubes 63, which are arranged in an oxygen collection chamber 64 in the lower part of the upper column, the lower ends of these tubes are in communication with the upper end of the rectification chamber 60 and the upper tubes open into an end cap 65. An annular protruding trough 66 below the outer condenser tubes, high-purity liquefied nitrogen collects from these tubes. Part of the nitrogen liquid is supplied via a nitrogen line 67 controlled by a throttle valve passed into the upper end of the column 61 to form a reflux liquid for the upper column. The remaining liquid oxygen drips back into the upper end of the lower column 60 in order for this one Provide return liquid.

A first section for the rectification of the scrubber-washed air in the rectification chamber 60 is used in a known manner to obtain essentially pure liquid nitrogen, which is produced by the Line 67 is withdrawn and a substantially oxygenated liquid at the bottom the chamber 60 is realized. These fluids are mixed with purified scrub fluid and cooled, purified air vapor from the suction of the turbine 57 to the upper column forwarded, the air vapor of the upper rectifying column 61 through in adjustable amounts a steam inlet line 71 is fed at a point in the middle of this column. The scrubber fluid in a line 72 which has previously been filtered in a filter 25 and enriched with oxygen Increased air from the lower column via a line 73 with an interposed throttle valve enters the upper column between lines 67 and 71 for the liquid nitrogen or the air vapor.

As a result of the rectification process in the upper column 61, oxygen gas can lower Approximately 95% purity oxygen near the bottom of the top column at a point a little way up the chamber 64 can be withdrawn through an oxygen removal line 75. In the chamber 64 is practically pure, the main condenser 62 surrounding liquid oxygen obtained and collected from this chamber can be drawn off via a line 76 and fed into the secondary condenser 28.

The gaseous nitrogen outflow resulting from the rectification process in the upper column 61 is removed from the top of the column via line 80 and to nitrogen heat exchanger 78 sent, where it is heated in countercurrent against the liquid nitrogen of higher pressure in line 67 will. At the same time, the liquid nitrogen in the line 67 is before its expansion through the throttle valve 68 further cooled.

The nitrogen gas exiting heat exchanger 78 flows through lines 81 and 82 to the liquefaction coil 22 in the scrubber 17 in order to utilize its cooling effect and around it at the same time to guarantee. to overheat at maximum regenerator capacity.

The secondary capacitor 28 comprises a large number of parallel narrow metal tubes 84, preferably Copper, held together by means of perforated tubular sheets 85 arranged on the top and bottom of the tubes will. A copper cap 86 with a line 88 is located above the tubes 84 for high-purity oxygen gas for taking up vaporized oxygen gas from the secondary condenser. Below the tubes 84 there is a collecting container or oxygen chamber 87 for receiving the liquid oxygen from line 76 for high purity oxygen. By introducing the scrubber air vapor it in line 27 into the space around the tubes and between plates 85 and boiling of the liquid oxygen in the collecting container 87 of the condenser, oxygen is evaporated and flows through the tubes 84 of the side capacitor and into the cap 86.

Although according to the description above, the use of the scrubber-washed air outside of the tubes 84 and the liquid oxygen in the oxygen chamber 87 is provided as the sub-condenser equally suitable for a reverse application, i. H. with the washed air inside the tubes and the liquid oxygen outside them. On the other hand, you can also take precautions taken to nitrogen gas from the lower column instead of scrubbed air vapor to use to evaporate the liquid oxygen in the secondary condenser, or the secondary condenser 28 can be omitted, and its functions are taken over by the main capacitor 63, which then would have to be enlarged accordingly.

The exiting from the cap 86 of the secondary condenser high purity gaseous oxygen with an oxygen content of about 99.5 ° / ₀ or more flows through the line 88 with the interposed control valve 89 to and through the channel for heating the high-purity oxygen to the in the Countercurrent heat exchange channel 50 to precool high pressure air entering, wherein a greater part of the cooling effect of the cold high-purity gaseous oxygen is recovered.

It is clear that under the given start-up conditions, the steam expanded in the turbine 57 cannot be completely free of harmful substances such as carbon dioxide, since the initial cooling and the scrubber liquid available in the scrubber 17 is insufficient to remove these contaminants. For this reason, carbon dioxide can get into the rectification system and possibly the Adversely affect the separation process. In order to avoid this state that occurs during the start-up process

avoid, an interrupter valve 124 and a secondary line controlled by means of valve 92 are provided for branching off and diverting the turbine-cooled air in line 71 through nitrogen gas line 82, coil 22 and through nitrogen regenerators 14 or 15 as waste gas. As soon as sufficient cooling and liquid are available in scrubber 17 and suitable permanent conditions are created so that the supply of pure steam from the cap part is ensured, valve 124 can be opened and the pure steam, expanded in the turbine in line 71, is directly fed into the upper rectifying column 61 sent.
When valve 92 is closed and valve 124 is open, the operating conditions are in place for maximum gaseous oxygen recovery by the system. If only the system with low air pressure is used without liquid recovery, the liquid passed on from the main condenser to the secondary condenser is preferably passed through a _{separator (not shown) which adsorbs CO 2} and hydrocarbons and advantageously contains silica gel.

For a high recovery of liquid oxygen and a low recovery of gaseous oxygen can the gas flow in the lines 88 and 75 by means of the throttle valves 89 in the line 88 and the valve 150 in the line 75, which in each case the extraction of the gaseous oxygen control high and low purity. The liquid oxygen in the collecting container 87 can preferably at the bottom of the side condenser 28 by means of a valve-controlled line 93 for the high purity liquid oxygen can be withdrawn. Accordingly, from the chamber 64 of the main condenser liquid oxygen can be withdrawn. During the extraction of large quantities of liquid Oxygen processed the upper column 61 a larger amount of gas, and because of the limited capacity In the column, an increase in the back pressure on the expansion turbine 57 can occur. this however, it is undesirable because this reduces the cooling effect of the turbine; consequently the bypass valve 92 is opened to vent some or all of the expanded air so that on in this way the turbine back pressure is reduced and the turbine cooling is increased. According to this Procedure is a relatively larger amount of liquid air in the liquefaction section of the Scrubbers 17 won, which in this way withdrew the liquid oxygen during the extraction Cooling compensated.

Is a 'simultaneous extraction of liquid and If gaseous oxygen is desired, these products can be extracted from their corresponding products in a simple manner at the same time Remove lines 75, 88 and 149 in any desired amount, which is determined by appropriate Adjustment of the nozzle valves of the turbine 57, the secondary line 92 and the valves 150 and 89, respectively or 93 is selected.

It can be seen that with the present arrangement of the double cooling sections 50 and 53 present certain limitations on the operating conditions. That part of the gas which is under a pressure of 5.27 kg / cm ² and is washed in the scrubber, which is not required by the column to ensure optimum purity, is expanded in the turbine 57 to obtain external work. As mentioned above, it is desirable to heat this scrubbed gas with high pressure air in the coil 53, so that a subsequent liquefaction in the expansion turbine 57 is avoided in this way. Accordingly, a sufficient amount of high pressure air must be circulated to heat the oxygen and nitrogen in passages 51 and 52, respectively, of countercurrent heat exchanger C and the scrubbed gas in coil 130, respectively. Appropriate distribution of the high pressure air is ensured by working expansion of the remainder in machine 47.

In a modified embodiment according to the. Fig. 2 form the functions of the scrubber 17 and of the secondary condenser 28 is part of the double rectification column.

2 shows a double rectifying column 95 with an upper column 96, a main condenser 97 and a lower column 98 which essentially have the parts shown in FIG correspond. The lower column 98 is extended, however, to the essential requirements for a to create appropriate scrubbing activities. Instead of the cooled air vapor of the line 20 in the With this arrangement, scrubbers can pass the air through an oxygen-rich liquid air Scrubber bath are passed into the extended or kettle portion of the lower column 98, by simply sinking it directly into the bottom of this part. This air flows through the scrub liquid and emerges as clean, washed air vapor, which as it rises in the column in in exactly the same way as the air vapor is rectified in the lower column 60 illustrated in FIG will. The main advantage of the lower column, which forms a whole with the scrubber, lies in the lower manufacturing costs.

In addition, the lower column fulfills its scrubber functions by feeding scrubber liquid to the upper column 96 through a line 23 with a control valve 24 and a filter system 25, 25 _a similar to that shown in FIG.

A comparison with FIG. 1 also shows that that the washed-out air vapor for the turbine preheating exchanger 53 by means of the air vapor line 99 is fed with a control valve 100, the Line 99 is in communication with the lower column. Part of the pure steam in line 99 is via branch line 104 into a liquefier 101 with oxygen and nitrogen liquefaction coils 102 and 103 correspond to the liquefaction coils 21 and 22 of Fig. 1 derived, which the condensed treatment liquid leads through a return line 105 due to Eigengewjchtzuspeisung in the lower column. The purpose of the condenser 101, which is separate from the collecting tank 127 for structural reasons, is generally to the effect of sufficient over-

heating of the separation products for the efficient operation of the regenerators 12, 13, 14 and 15.

From the upper column 96, low-purity gas is obtained by means of the oxygen withdrawal line 75 such as subtracted in Fig. ι and the liquefaction coil 102 fed where there is sufficient for the subsequent passage through line 31 to the oxygen-cooled Regenerators 12 and 13 is heated. As a common means of obtaining High purity oxygen in both liquid and gaseous state without secondary condensers to achieve these functions, liquid oxygen is drawn from the bottom in adjustable quantities Chamber 64 in the upper column 96, e.g. B. by means of a line 106 controlled by a valve roy, removed while high purity gaseous oxygen from the upper column '96 at a point so close as possible and above the level of liquid oxygen in chamber 64 through conduit 108 for high purity gas is withdrawn.

The use of the capacity of the high purity gas in line 108 for cooling is different from that of the corresponding gas in line 88 of FIG. B. the countercurrent channel 50 of FIG. 1, in heat exchange with the nitrogen-cooled regenerators 14 and 15 through the coolant laid in the regenerator walls, namely the cooling coils 110, one of which is preferably provided for each regenerator, by means of the line in for high-purity oxygen connected to line 108 and controlled _{by valves 109 and iog a.} Notwithstanding this, the oxygen coils can also be wrapped around the outside of the regenerator body. The oxygen flow in the cooling coils 110 can either be continuous, or provisions are made to switch the flow alternately between the regenerators 14 and 15. In the present embodiment, a continuous oxygen flow is used in the cooling coils 110 are preferred.

It is clear that because of the use of the high purity oxygen gas as an additional coolant in regenerators 14 and 15 the need for a three-way countercurrent heat exchanger, such as B. the heat exchanger 50 in Fig. 1 is omitted. Accordingly, the illustrated in FIG Cycle processes these heat exchange media through a cheaper and more powerful one Replace two-way countercurrent heat exchanger 112 which uses high pressure air from the precooler 44 in passage 113 against the counter-flowing, separated nitrogen gas product in line 54, flowing through line 114 is cooled. It is further evident that because of the application of the Auxiliary oxygen coolant in regenerators 14 and 15 will determine the amount of oxygen produced by these regenerators flowing nitrogen gas and the gas flow in line 114 can be increased accordingly can.

As another possibility for direct feeding of the high-purity oxygen gas into the lines 110 of the regenerators and in particular to avoid partial oxygen liquefaction in the cooling coils of the regenerators, the high-purity gas in the line 108 can be heated to approximately the temperature of the regenerator nitrogen by means of a branch line 115 with a valve H5 _a , which is shunted to the control valve i09 _o and is connected to one end of a condensing coil 116 in the condenser 101, the other end of which is on the opposite side of the valve i09 _o via a line 117 with the line in connection. By setting the valve iO9a _, some or all of the high-purity oxygen can be passed through the liquefier 101 and brought to a suitable temperature for the subsequent heating in the regenerators 14 and 15 with the oxygen and nitrogen gas in the coils 102 and 103.

In the event that high purity liquid or gaseous products are desired under a higher pressure than that prevailing in the upper column 96, a machine 118 can be provided to receive these low temperature products at low pressure and dispense them under higher pressure. If a high pressure liquid product is desired, the machine expediently has a pump, preferably a reciprocating immersion pump. In this case, liquid flows through the valve-controlled line 121 to the pump suction under low pressure, e.g. B. 0.21 to 1.4 kg / cm ² , and is under higher pressure, e.g. B. 1.76 to 211 kg / cm ² , via the line 120 leading to the trigger valve 125. If a gaseous product of higher pressure is desired, the machine 118 can have a gas compressor, and the low pressure gas from the line 108 can be diverted through the valve 109 via the connection 119 to the compressor 118, from which it exits under higher pressure and then into is passed through the cooling system in the manner described above.

In another embodiment preferred for the production of high-purity gaseous oxygen at high pressure, the machine 118 expediently has a liquid pump, as described above, the secondary line 119 being provided for ventilating the vapors developed in the pump back into the chamber 64. Rather than deliver the liquid at the terminal 125, the high pressure oxygen, through the open valve IO9 _a, the line and in the heating duct 110 is guided to be discharged in order to then from this as a high purity oxygen gas product under high pressure.

The means for varying the relative amounts of the leakage of liquid and gas according to FIG. 2 are essentially the same as in Fig. 1, except that different means of withdrawing the in the scrubber washed gas from the column for subsequent preheating and turbo expansion are installed. These means include a nitrogen gas line 122 for venting uncondensed nitrogen gas from the Cap of the main condenser 97 and a valve 123 for controlling this gas flow into the inlet line 99

the turbine heating coil on. An advantage of this approach is the greater assurance that clean gas is entering the turbine, as some CO ₂ or hydrocarbon could possibly be carried over if the gas is at a lower point in the column, e.g. B. 4n the line 99 is deducted. On the other hand, there may be a slight loss of separation efficiency.

More turbine inlet nozzle valves are opened to increase liquid recovery and decrease gaseous oxygen recovery. Thus, the valve 92 can be opened sufficiently to allow a desired amount of the expanded air to be diverted through the conduit 82, thereby reducing the turbine back pressure. At the same time, the recovery of low-purity gas is reduced by partially closing the valve 150, while the recovery of high-purity, gaseous oxygen is decreased to the desired extent by partially or completely closing the valve 89 or 109. The desired amount of liquid recovered is withdrawn through valve 93 (FIG. 1) or through line 106 (FIG. 2) by adjusting valve 107 or actuating pump 118 (FIG. 2) to remove liquid from the Withdraw line 121 and deliver it through line 120 and port 125 at the desired pressure. Conversely, the liquid recovery is reduced and the gas recovery is increased by adjusting the valves in the opposite direction. In any case, in the embodiment according to FIG. 2, the steam for reheating in the exchanger channel 130 and expansion by the turbine 57 can be withdrawn from the high-pressure chamber 98 of the column either via the line 99 or the line 122. Each embodiment can be set for the production of only oxygen as well as liquid alone, in that the high pressure compressor 40 operates at maximum volume and high pressure, the oxygen regenerators 12 and 13 closed, the bypass valves 92 open wide for the expanded air, the valves 124 closed, the Valves 150, 89 or 109 (Fig. 2) for gaseous oxygen are closed and the liquid oxygen product is withdrawn at 93 (Fig. 1) or 107 (Fig. 2). When the valve for high-purity oxygen is closed in FIG. 1, all of the oxygen evaporated in the tubes 84 of the condenser 28 is fed back into the column 61 through the line 91. This reduces the amount of low pressure air and increases the amount of high pressure air generated. To compensate for the heat exchange, the proportion of the nitrogen flowing out through the countercurrent exchange channel 52 (Fig. 1) or 114 (Fig. 2) is increased, while the amount of nitrogen flowing through the regenerators is increased by adjusting the valve 32 _O in the branch of the line 32 which leads to the regenerators 14 and 15 is reduced.

This procedure described immediately above can be modified in a simple manner to obtain a portion of high-purity gaseous oxygen by simply opening valve 89 (FIG. 1) or valve 109 (FIG Allow amount to pass, and that the opening of the valve 32 _{a is} slightly adjusted to create the heat exchange conditions.

For maximum gas recovery and low liquid recovery, the compressor 40 is operated at low volume and under a low discharge pressure, e.g. B. 84.3 kg / cm ² . The low pressure air is cooled in both oxygen and nitrogen regenerators. A smaller part of the air under a pressure of 84.3 kg / cm ² is expanded in the expander 47 in order to ensure adequate heating of the turbine air in the exchange duct 130. The amount of air expanded by the turbine 57 is determined by closing some nozzle valves is reduced, and the entire effluent is released by opening the valve 124 and closing the bypass valve 92 to the rectification column. The low-purity oxygen valve 150 is open and the high-purity gaseous oxygen valve 89 or 109 is adjusted to withdraw the desired amount of high-purity oxygen. Liquid oxygen valves 93 (Fig. 1) or 107 (Fig. 2) are adjusted to withdraw a smaller amount of liquid oxygen in order to maintain an appropriate level of liquid in chamber 64 of the rectifying column. The heat exchange is compensated for by adjusting the valve 32 _O.

If it is desired to withdraw at least a small portion of the liquid oxygen, the Fluid recovery reduced to insignificant levels with a small sacrifice in overall performance are achieved by a further reduction in the air part compressed to high pressure and corresponding Enhancement of the low pressure air flow. In the illustrated embodiments it is necessary to send enough air through the heat exchange duct 53 to meet the heat demand for to correspond to the turbine air heating duct 130.

A maximum total production of oxygen is achieved by obtaining a desired proportion of the amount of total oxygen in the form of high-purity oxygen, obtaining low-purity oxygen in an amount of about 90% of the amount in the previous example and obtaining a small amount of liquid oxygen achieved. Approximately the same amount of air is compressed to a higher peak pressure of about 140 kg / cm ² , which causes the increasing cooling to the low temperature of the increased liquid recovery. In this case, some of the air expanded in the turbine is sent to the rectification column and some is diverted by adjusting valves 124 and 92, the ratio being greater than 2: 1. A larger total amount of air is also expanded through the turbine.

It is about the adaptability and suitability of the system to the changing demand for oxygen products To illustrate, four examples of operating conditions are given in the following tables.

Example ϊ Volume I pressure

Example 2 Volume I pressure

Example 3
Volume I pressure

Example 4 Volume I pressure

a) (in ii).

b) (in 19).

c) (in 18).

d) (in 41).
(in 48).

f) (in 50).

g) (in 20).
(in 26).
(in 56)
(in 73)

k) (in 72).
1) (in 67).

(in 71).

(in 92).

(in 75)
p) (in 88).

q) (in 93)
r) (in 81).
s) (in 32).

t) (in 54)
u) (in 32 a)
v) (in 31).

)
e)

)
i)
j)

m)

n)
O)

62.4 37.0

23.3 11.0

12.3 60.4

17.7 29.8 6.40 12.8 10.9

29.8

24.2 54.0 15.6 38.9

5.98 5.98

140.6 5.84 140.6

5.55

5.55

0.70

7.79
3.12

4.67
59.6

42.1
4.58
6.96
5.24

5.28
5.28

140.6
5.20
140.6

4.78
4.85

0.56

62.4

44, i
7.61

7.79
3.29
3.43
59.6
32.2
16.2

15.1
11.2

17.0

11.3
4.37
8.02
0.80

1.95
43.8
43.6

3.23
45.6

0.80

5.77 5.77 5.77 140.6

5.35 140.6

5.28 5.28

o, 49

62.4 38.4 84.9 7.79 25.2

5.27 54.7 32.2 12.6

15.1 9.95

I7, i 12.6

8.92

o.99 0.96

43.8 43.8

4.47 39.4

8.92

5.55 5.55 5.55

84.3 5, i4

84.3

5, o6 5.14

0.42

Volume in m ³ . Pressure in kg / cm ² above atmospheric pressure.

example 1

For the production of high-purity liquid oxygen and no production of gaseous oxygen of high or low purity, the high-pressure compressor working with an ^{outflow under a pressure of kg / cm 2} and three times the amount of Examples 2, 3 and 4 and the rectification column with a moderate Production figure.

Example 2

For the production of only highly pure liquid oxygen and no production of gaseous oxygen of high or low purity, the high-pressure air compressor working with an ^{outflow under a pressure of kg / cm 2} and a third of the amount of Example 1 and the rectification column with a low production figure.

Example 3

For the production of about 18 ° / ₀ high purity liquid oxygen, 8 ° / "high purity oxygen gas and 74 ° / ₀ low-purity oxygen gas, with the high pressure air compressor at a pressure of kg / cm ² and a third of the amount of example 1 works and the rectification column with a high production rate.

Example 4

For the production of approximately 9 ⁰ Z ₀ high-purity liquid oxygen, 9% high-purity oxygen gas and 82% low-purity oxygen gas, the high-pressure air compressor with an ^{outflow under a pressure of 84.3 kg / cm 2} and a third of the amount of example 1 works and the rectification column with a high production rate.

In the table, the letters a) to v) relate to certain points in the circuit, which are briefly explained below, with the flows given in rounded numbers representing comparable flows in m ³ per unit of time at normal gas pressure and temperature, the pressure in kg / cm ² above atmospheric pressure and the production figure is expressed in its entirety.

a) The entire pressure of the low pressure air flow compressed air inlet.

b) Air after passing through the nitrogen regenerators 14 and 15.

c) Air after passing through the oxygen regenerators 12 and 13.. ¹⁰ p

d) Part of the air further compressed to the pressure of the high pressure air flow.

e) Part of the high pressure air expanded by machine 47.

ΐ) In 50 and 53 cooled and at the valve 55 "° throttled high pressure air flow.

g) Total inlet air of all streams into the scrubber [approximate total of b), c), e) and f) or h), i) and k)].

h) Air vapor fed to the lower column 60 and washed in the scrubber.

i) In 130 rewarmed and the turbo-expander 57 supplied washed air vapor.

The feeds into the upper or lower pressure rectification column:

j) Impure oxygen from lower chamber 60.

k) scrub fluid from 17 after cleaning through the filter 25.

1) Liquid nitrogen from trough 66.

m) Expanded air from the turbo expander 57.

n) Through valve 92 to line 82 for exhaust

flowing nitrogen diverted part of the expanded Air.

Products from the upper column 59:

o) Gaseous oxygen of low purity (95 ° / ₀ ) in line 75.

p) Highly pure (99.5%) gaseous oxygen withdrawn through line 88.

q) Liquid oxygen (99.5% purity) withdrawn through valve 93.
r) Nitrogen flowing out of the top of the column.

s) Sum of the excess air η) and the nitrogen outflow r).

t) The proportion of the combined outflow which flows through the countercurrent heat exchange channel 52 _{as regulated by the valve 32 O.}

u) The through the nitrogen regenerators 14 and 15 flowing part of the combined emanation.

v) The low purity oxygen flowing through the oxygen regenerators 12 and 13.
The above examples relate to the system according to FIG. 1, but can also be applied equally to the modified system according to FIG. 2. In either embodiment, the compressor 40 can be arranged so that the pressure of the high pressure air is increased to over 140 kg / cm ² , e.g. B. to 211 kg / cm ² , is increased, in which case the use of a precooler 44 can be dispensed with. The ability to increase the high pressure can also be used if it is desired to increase the liquid fraction in the oxygen recovery. The ratio of the volume of high pressure air used to the low pressure air depends on the production requirements. For example, the amount of data processed in a plant high-pressure air at 12 to 40 ° / ₀ of the total processed amount of air.

It can be seen that a major advantage of the present system is the ability to proportional amounts of the low pressure air flow and the high pressure air flow as well as the pressure of the the latter in accordance with the need for oxygen in the gaseous state to the need for to adjust liquid oxygen.

Claims (1)

PATENT CLAIMS: i. Process for the separation of low boiling points Gas mixtures by rectification at low temperature, at which gas mixture flows below Condensation pressure as well as high pressure are provided, with the stream under condensation pressure cooled by heat exchange with part of the separation product to a temperature close to its condensation temperature is, while a first part of the high pressure flow is cooled by expansion work to the condensation pressure and a second part of the High pressure flow through heat exchange including a heat exchange with a other part of the separation product is cooled to a low temperature and that on this Way, cooled second part expands to the condensation pressure and a partial liquidation of the vapor parts of the resulting streams is effected under condensation pressure, to ensure the liquid supply for the rectification, characterized in that the non-liquefied remainder is superheated to such a temperature that it is after expansion work is in a dry, saturated state under rectification pressure and then the superheated steam expands, as well as that the proportional release of the gaseous and liquid separation products by passing on set amounts of the expanded vapor for rectification as well as for the outflowing, lower-boiling product of the rectification is controlled and / or by Regem the proportional amount of the supplied under high pressure Gas mixture to the supplied under condensation pressure. 2. The method according to claim 1, characterized in that that the proportional release of gaseous and liquid separation products additionally through Change of the feed pressure of the gas mixture is controlled at high pressure. 3. The method according to claims 1 and 2 for the separation of air, in which the gaseous separation product is withdrawn in a larger amount than the liquid separation product, characterized in that the entire expanded vapor is fed to the rectification and that the gas mixture fed under high pressure under a pressure of not more than 140 kg / cm ² above atmospheric pressure. 4. The method according to claims 1 and 2 for the separation of air, in which the gaseous as well as the liquid separation products are withdrawn in a substantial amount, characterized in that for a maximum total production of all expanded steam is passed on to the rectification and that under high pressure The gas mixture fed in is under a pressure of at least 140 kg / cm ² above atmospheric pressure. 5. The method according to claims 1 and 2 for the separation of air, in which only the gaseous separation product is withdrawn, characterized in that all the expanded steam is fed to the low-boiling rectification product flowing out and that the gas mixture fed in under high pressure under a pressure of 140 kg / cm ² or more above atmospheric pressure. 6. The method according to claims 1 and 2 for the separation of air, in which only the liquid separation product is withdrawn, characterized in that all expanded steam is fed to the rectification and that the gas mixture fed under high pressure under a pressure between 140 and 211 kg / cm ^{2 is} above atmospheric pressure, the amount added being sufficient to carry out the rectification at maximum capacity for the recovery of liquids. 7. The method according to claims 1 and 2, characterized in that the second part of the high pressure Stream of the gas mixture cooled by heat exchange with the non-liquefied remainder and with the cooled gas mixture is combined at condensation pressure. S. The method according to claims ι and 2, characterized in that the second part of the high pressure flow of the gas mixture is cooled with a certain amount of a separated product proportional to the amount of the second part of the high pressure flow and thereby an adequate remainder for cooling the gas mixture flow fed in at the condensation pressure forms. 9. The method of claim 7, wherein the combined stream with a liquid portion approximately is washed out at condensation pressure to form a purified vapor, · also impurities of the liquid fraction used are removed, further at least part of the washed vapor is subjected to liquefaction to form liquid fractions, and the liquid fractions are fed to the rectification, characterized in that the non-liquefied steam washed in the scrubber undergoes heat exchange with another high-pressure stream is subjected, the superheated steam washed in the scrubber is brought to rectification pressure by expansion work and the Cooling of this expansion is used to achieve at least part of the liquefaction will. 10. The method according to claims 1, 2, 7, 8 and 9, in which the liquid rectification product of high purity is collected, at least a part this product evaporates and at least part of the resulting steam is used for rectification is returned where the composition is essentially the same, characterized in that that the recycle of the high purity steam for rectification is consistent is changed with the amount of the high purity gaseous product withdrawn. 11. Device for carrying out the method according to claims 1 to 10 with compressor means for supplying separate streams of a Gas mixture at a condensation pressure and a high pressure, furthermore with a heat exchanger for the purpose of using separation products for cooling the gas flow at condensation pressure, an expansion machine for the cooling of a first part of the high pressure stream, further with a heat exchanger for Purpose of using another part of the separation products for cooling a second one Part of the high pressure flow, with expansion valves to expand this second part Condensation pressure and corresponding generation of liquid, as well as with lines for guiding this liquid as a feed liquid to a rectification column, characterized by heat exchange means (130) for overheating the non-liquefied residue, an expansion machine (57) for expanding and cooling this non-liquefied residue and a branch line system with Valves (92, 124) for controlling the respective flow of the expanded refrigerated residue to a Place of appropriate composition in the rectification as well as for the outflowing lower boiling point Product. 12. The apparatus of claim 11 having a Compressor for compressing the entire gas mixture supplied at condensation pressure, characterized in that the outlet of this compressor with lines divided into branches is connected, one branch of which is connected to a multiple compressor (40) for compressing the said second stream to a predetermined high pressure and volume connected is. 13. Device according to claims 11 and 12 with lines for withdrawing a high-purity boiling product from the lower area of the Rectifying column and a low-boiling gaseous product from the upper area this column, characterized by countercurrent heat exchanger (C) with a channel (50) for the cooling of at least part of the high pressure gas feed stream, a channel (52) for receiving and heating part of the withdrawn low-boiling product and a channel (51) for absorbing and heating the higher-boiling product without contamination of the same. 14. Device according to claims 11 and 12 with lines for withdrawing a high-purity, higher-boiling product from the lower area of the Rectifying column and a low-boiling gaseous product from the upper part of this Column characterized by a countercurrent heat exchanger (112) with a channel (113) for cooling at least part of the high-pressure gas feed stream and a channel (114) for receiving and heating part of the withdrawn low-boiling product, also by regenerators (14, 15) for cooling the at Condensation pressure fed gas stream to take up the remainder of the low-boiling product and by heat exchange channel means (110) connected to the regenerators for the purpose of absorbing and heating the product of high purity without contamination same. For this purpose ι sheet of drawings ö 609 657/134 10.56 (609 853 3. 57)